How to Instantiate a PreFab only once

Archived Forums Questions & Answers
1

I am trying to make a +1 life object and corresponding functions. I can make it appear where and when I want to. What I am having trouble with is that using this code:

Instantiate(PlusOneLifePreFab,Vector3(0,2.5,75.6), Quaternion.identity);

When I use this it creates endless clones. By having a destroy script I am able to keep the clones to a manageable number, but the lowest number of clones I can get down to is two. Ideally, I would only like to have only one object spawn in my world, but I can’t figure out how to do it.

Help appreciated.

4 Answers

4
3

Are you creating the instance inside a an update function?

If so you need to only allow the creation once.
There are different ways to do this, the simplest would be to create a boolean and only create it if the boolean is true.

Something like:

var isCreated: boolean;

function Update(){
    if(!isCreated){
       Instantiate(PlusOneLifePreFab,Vector3(0,2.5,75.6),Quaternion.identity);
       isCreated = true;
    }
}

For JavaScript anyway. There are other methods as well, such as using the Awake() function.

Hope this helps.

So wait, how do you set isCreated to false when the object is destroyed?

 –

Nice work with c#. Just change var to bool. bool isCreated ; rest is same in both languages. If anyone still unable to Understand.

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2

I bet you are doing this in an Update function right? Don’t do that. Or have a variable you set when you create one, and check it before you make it (again)

Why not just do it in a Start() routine? Only do it in Update if it is in response to something dynamic. Putting it in a case won't make much difference (assuming you coded it right).

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4

You have said in a comment that your Instantiate function is nested with a switch case statement, right?
It looks like you have forgot to have a “do nothing” case in your switch case statement

int option = -1;
Update()
{
        switch (option)
        {
                case -1:
                        break;
                case 0:
                        Instantiate( ... )
                        option = -1;
                        break;
        }
                

}
public void DoInstantiate()
{
        option = 0;
}

If you don’t have a dummy case and you don’t update the switch variable to the “do nothing” case (-1 in my example) at the end (before of the break) of an action, it will result in repeating the same action every frame, constantly, until the switch variable changes.

5

GameObject CityClone;
public GameObject CityPrefap;
public GameObject CityPosition;

// Start is called before the first frame update
public void Create()
{
    if (CityClone == null)
    {
        CityClone=Instantiate(CityPrefap,CityPosition.transform.position,CityPosition.transform.rotation);
    }